When the HSS left Stranraer (Scotland) on its way to Belfast, when it was in Stranraer bay passengers heard a big crash, which was the lorry crashing into the stern ramp. it had to head back to port.
I believe the MAIB (Marine Accident Investigation Branch) will be doing a investigation. Not sure on this though.
There is info here = http://forum.shipais.com/index.php?showtopic=2345